1. Field of the Invention
The present invention relates to a vehicle theft prevention device. More particularly, the present invention relates to a vehicle theft prevention device by which a vehicle can be surely prevented from being stolen when unlocking of a vehicle door and unlocking of a vehicle drive system are separately conducted.
2. Description of the Related Art
Conventionally, it is common to use a key when a vehicle door is locked and unlocked. However, when the above door locking and unlocking method using a key is adopted, there is a high possibility that the vehicle is stolen because a door can be unlocked, with criminal intent, using a copied key or special tool such as a picking tool.
In order to solve the above problem, a keyless entry device, the theft prevention property of which is high, has been recently put into practical use. This keyless entry device is composed as follows. An identification code is stored in a control unit mounted on a vehicle. When the identification code and a command for locking or unlocking a door of the vehicle are transmitted from the outside of the vehicle to the control unit by a remote controller, the door can be locked or unlocked. In this way, a key hole in the door is not needed. Therefore, the occurrence of vehicle theft can be surely prevented.
In the above keyless entry device, when an unlocking operation of the door is conducted with the remote controller for opening and closing the door, a door unlocking signal is sent from the remote controller and received by the control unit mounted on the vehicle. The control unit collates an identification code, which is contained in the thus received door unlocking signal, with an identification code stored in a memory of the control unit itself. When the identification code, which is contained in the thus received door unlocking signal, is coincident with the identification code stored in the memory of the control unit, the door can be unlocked.
However, even in the case of a vehicle equipped with the above keyless entry device, it is impossible to prevent the vehicle from being stolen in the following cases. In the case where a key is stolen, or in the case where an identification code of the key is decoded by a decoder so that a copied key is made, or in the case where a door is forced to open, it is impossible to avoid of theft of the vehicle.
As a means for solving the above problems, there is provided a vehicle theft prevention device in which locking and unlocking mechanisms are provided in both the vehicle running system and the vehicle door opening and closing system, and only when a driver unlocks the door with a remote controller, can unlocking of the door and unlocking of the vehicle running system be simultaneously conducted. When the vehicle theft prevention device of the above proposition is adopted in a vehicle, in the case where a person breaks into the vehicle by illegally forcing the door open, as the running system of the vehicle is still locked, it is impossible for the person to drive the vehicle. Therefore, theft of the vehicle can be prevented.
However, in the above vehicle theft prevention device in which locking and unlocking mechanisms are provided in both the vehicle running system and the vehicle door opening and closing system, the following problems may be encountered. As the door of the vehicle is unlocked and the running system of the vehicle is unlocked at the same time by operating the remote controller, in the case where a driver leaves the vehicle after the driver has unlocked both the door and the vehicle running system with the remote controller, the vehicle may be stolen by an intruder into the vehicle.